Process of purifying metals.



UNITED STATES PTENT OFFICE.

HENRY M. CHANCE, OF PHILADELPHIA, PENfiSYLVANlA.

PROCESS OF PURIFYING METALS.

Specification of Letters Patent.

Patented Oct. 3, 1905.

Application filed June 2, 1905. Serial No. 263 396.

To all whom it may concern.-

Be it known that I, HENRY M. CHANCE, of No. 819 Drexel Building, in the city of Philadelphia and State of Pennsylvania, have invented a certain new and useful Process of Purifying Metals, whereof the following is a specification.

Broadly speaking, processes for the purification of metals may be classified as follows, viz: those whereby the impurities are removed from the metal and those whereby the metal is removed from the impurities. In the former class the metal is exposed to the action of substances having a chemical affinity for the impurities which are to be removed. In the latter class the separation may be affected by volatilization or by electrolysis of the metal and its redeposition.

My present invention relates to the firstmentioned class of processes, in which chemical afiinity is the underlying principle. In carrying out these processes where the purifying substances usually consist of or are contained in gases, fused slags, or solids it is often diflicult to obtain the most desirable reagent and to preserve, store, and handle it in its most efficient condition, and there is also often diflficulty in bringing such reagent into intimate or molecular contact with the impurities themselves. My process is in- .tended to overcome these difiiculties; and to that end it consists in developing or disengaging the purifying reagent by electrolytic action in immediate contact with the metal to be purified in a state of fusion. '1 thus obtain the double advantage of increased chemical aflinity, due to the nascent condition of the disengaged substance, and of insuring the most intimate contact with the impurities themselves. Moreover, I am enabled to employ reagents which cannot well be used under other conditions, because of the difiiculty of obtaining, preserving, and applying them in what may be termed a permanent free state and also because of the difliculty of controlling their action accurately when added on 12 08812 to the metal to be purified. It is of course a characteristic of my invention that the reagent thus electrolytically disengaged should have at the temperature used greater chemical affinity for the impurities than it has for the metal to be purified. The process may be operated in an ordinary electrolytic cell adapted to contain a fused electrolyte in contact with a fused metal, and hence I do not deem it necessary to describe in detail any particular type of apparatus.

In carryingout my process the fused metal is maintained in contact with a fusedelectrolyte containing the desired reagent and is connected, as one of the poles, to a source of electric energy, the other pole being placed in contact with or partly immersed in the fused electrolyte. The passage of the electric current sets free the purifying reagent in a nascent state from the fused electrolyte at its region of contact with the fused metal, and the element or elements thus set free combine with the impurities contained in the fused metal, forming chemical compounds of such impurities, which may remain suspended or dissolved in the electrolyte or if volatile may pass off as gas or vapor.

The metal to be purified may be fused in a crucible or any suitable furnacesuch as an open-hearth, reverberatory, or electr1c furnaceand is subjected to the described treatment with the electrolyte floating upon it if the specific gravity of the metal be greater than that of the electrolyte, or vice versa if the reverse be true.

My process is not a process of electrolytic purification, but merely uses electrolysis incidentally, and itdiffers from the ordinary electrolytic processes employing fused elec trolytesin that the cell is not used for the production and recovery of metal, but for the pulrification of fused metal forming one of the po es. processes, because the metal to be refined or purified is not dissolved by the electrolyte and-redeposited on the other pole. It also differs from refining of metals by direct electrolysis of the impurities, (as is aimed to be done by some processes,) because the purification of the metal in my process is effected by the action of elements contained in the electrolyte, which are set free in a nascent It differs from electrolytic refining state by the electrolysis of the electrolyte at .iron or steel being made the cathode, the

electric current freeing in a nascent state calcium or other metal of-thegroups mentioned at or upon the surface of. the iron or steel.

' Such disengaged metal immediately combines with the carbon, phosphorus, sulfur, oxygen,

, and othertimpurities for which it has great chemical afinity, to form carbids, phosphids, sultid's, .oxids and (other compounds, which are carried ofi by the supernatent electrolyte.

The processmay be used for the purification of copper from oxygen, sulfur, phosphorus. selenium,arsenic,and other impurities byusing an electrolyte similar to that described for purifying iron and steel, making the fused copper the cathode, the impurities being. removed as. oxide, sulfids, selenides, arsenides, and othersal'ts of calcium or other metal. of. the above-named groups. it may also be applied to the purification of copper and nickel. alloys, from sulfur, arsenic, and otherv impurities by applying the methods above described to be used for iron or .steel and copper. .lln this and similarapplications of, the process-salts (especially thehaloid salts) of. the alkalies and alkaline-earth metalscapable of electrolytic decomposition'when vfused are the most useful electrolytes, be-

- cause at. the temperature used these metals most readily combine with. and remove the elements that constitute most of the objectionable'impurities in metals such as sulfur, arsenic, oxygen, phosphorus, silic'on, tellurium, selenium, the halogens, and other elementsas before. specified.

The process mayibe used in removing me- .tallic impurities from metals and alloys by using an electrolyte of such character that the elements set free from it at the surfaceof the fusedmetal or'alloy have greater chemical. afinity for the metallic impurity than for the metal tobe -purified.as, for example, the removal ofiron from copper, which may be accomplished byusing an electrolyte'coutainving electrolytically-available oxygen, making the fused copper the anode and oxidizing the iron by the oxygen set free in a nascent state 6 at .the surface of the fused-copper anode.

The process may be also used in purifying metals from easily-oxidizable impurities by making the fused metal the anodeand using a fused electrolyte containing electrolyticallyavailable oxygen, which is set free in a nae cent state at the surface of the metal and selectively. combines with and removes easilyoxidizable impurities present, and similarly also by using a fused electrolyte containing electrolytically available halogens in cases where the chemical afinity of the halogens at the temperature used for the impurities to be removed is greater than their afiinity for the metal to be purified.

if the fused metal and impurities act as an electrolyte, and-if at the temperature used the impurities to be removed are electronegative elements, then the fused metal must bemade the cathode, and the impurities must be removed by generating in a nascent state from the electrolyte at the surface of the fused metal an electropositive metal preferably of the groups before named.

in cases where the metal to be purified is made the anode a small quantity of metal or clectropositive element will be deposited at the cathode, and while this is purely incidental this metal may often profitably be recovered, which may be accomplished by placing the cathode at one side of, and not vertically above," the fused metal to be purified and permitting the metal disengaged at the cathode (if fusible at the, temperature used) to drop ofi" into a depression in the fioor of the furnace vertically beneath the cathode, or the metal may be recovered in many other obvious ways. the same as the metal undergoing purification,

it'may be allowed to drop directly into the anode metal, or if it bea metal that can advantageously be added to such anode metal to form an alloy it may be allowed to drop ofi directly through the electrolytic bath into the anode metal. As the quantity of impurities to be removed is usually by weight only a small percentage of the metal to be purified, it is evidentthat any metal deposited at the cathode will be correspondingly small in quantity and will usually be of small economic importance, and such metal may be regarded entirely as a waste or by product and not essential to the working of the process; but the value of the metal so ,obtained, although small in quantity as compared with the metal being purified, if relatively highpriced, may largely decrease the net cost of operating the process.

The purification of many other metals and alloys may be effected by this process by the use ofproper electrolytes and by passing the electric current in the proper direction, as indicated by very simple rules, which will be readily understood by any one versed in the electrometallurgical art.

Among theimportant practical considerations are the following:

First. llfatthe temperature used the chemical afinity of oxygen, the halogens, or other elements set free from the electrolyte at the anode for the impurities to he removed be If such disengaged metal be greater than for the metal to be purified, the fused metal may be made the anode, and the electrolyte may be one containing electrolytically-available oxygen, halogens, or other described element.

Second. If at the temperature used the chemical afiinity of oxygen, the halogens, or other elements set free from the electrolyte at the anode for the impurities to be removed be less than for the metal to be purified, or if. it.

is not desirable to introduce into the metal to be purified any of these elements set free at the anode, then the fused metal should be made the cathode, and the active electrolyte should be a salt of a-metal having at the temperature used greater chemical affinity for the impurities to be removed than for the metal to be purified, this latter method also being applicable to metals containing impurities provided for in the preceding paragraph.

Third. 1f oxygen be one of the impurities to be removed, the metal to be purified may be made the cathode, and the electrolyte may be of1 the class described in the preceding paragrap 1.

Fourth. If the fused metal and impurities act as an electrolyte, then the fused metal must be made the cathode when the impurities to be removed at the temperature used are electronegative elements and must be made the anode when these impurities are electropositive elements. Under these last mentioned conditions any electrolytic action which may occur in the fused metal will facilitate the elimination of the impurities by bringing them to the surface of the metal, where an elemcnt for which they have great aflinity is being set free in a nascent state.

If the fused metal and its impurities do not act as an electrolyte, but merely as a conductor of electricity, the conditions described under the above clause marked Fourth need not always be observed; but in a majority of cases the best results will be reached by generating in a nascent state at the surface of the fused metal an electropositive element when the impurities to be removed are electronegative and an electronegative element When-the impurities to be removed are electropositive.

I am aware of the use of fused slags in electric furnaces in which the fused metal is made one pole and the other pole is immersed in the fused slag floating upon the fused metal, the

slag being used as a resistance for the purpose of transforming electric energy into heat and also of the use of two or more poles in contact with such slag and also of the use of electric currents passed through the fused metal to electrolyze and remove impurities from the metal; but my process differs from these in that it' requires the use of a fused electrolyte or electrolytic slag containing elements electroly tically available and set free at the region of contact of the electrolyte and metal, which elements at the temperature used have greater chemical aflinity for the impurities contained in the metal than for the metal to be purified, and which elements combining with such impurities eliminate them from the metal. In my process electrolysis is not used for the purpose of purifying or refining metal, but as a means to effect the generation at the surface of the fused metal of elements having at the temperature used a greater chemical affinity for the impurities to be removed than for the fused metal, and my sole reason for using electric energy is because this is the only manner by which I can produce upon the surface of the fused metal the required elements in a nascent state. My process is not intended to recover, as such, the metal or element which'is set free in a nascent state from the electrolyte upon the surface of the fused metal to be purified, and when in using my process an element is recoverable from the electrolyte the metal or element so reduced is a by-product and is disengaged not at the pole where the fused metal is being purified, but at the other pole.

I claim as my invention The process of purifying metal, which consists in maintaining the metal, in a fused condition, in contact with a fused electrolyte containing a reagent, which, at the temperature used, has greater chemical aflinity for the impurities to be removed fromsaid metal than it has for the metal itself; and electrolytically disengaging said reagent at the region of contact between the electrolyte and the metal.

In testimony whereof I have hereunto signed my name, at Philadelphia, Pennsylvania, this 1st day of June, 1905.

HENRY M. CHANCE.

Witnesses:

JAMES 'H. BELL, Jos. C. FRALEY. 

